CVE-2026-66307 json
Skype for Business and Lync Denial of Service Vulnerability
published 2026-09-08 2 mo ago modified 2026-10-31 8 d ago also EUVD-2026-73941
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 1.2%
- EPSS 1.2% chance of exploitation in 30 days, percentile 67%
- public exploits
- 0
- none known
Summary
Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a network.
Patch / fix
- Microsoft Skype for Business Server 2015 CU13 6.0.9319.885
- Microsoft Skype for Business Server 2019 CU8 7.0.2046.569
- Microsoft Skype for Business Server Subscription Edition CU1 7.0.2046.879
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 2 mo ago
Exploit prediction
1.17% chance of exploitation in the next 30 days, higher than 67% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C |
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected products
- Microsoft Skype for Business Server 2015 CU13
- Microsoft Skype for Business Server 2019 CU8
- Microsoft Skype for Business Server Subscription Edition CU1
Classification
- Weakness
-
- CWE-191 Integer Underflow (Wrap or Wraparound)
References
-
msrc.microsoft.com
/update-guide/vulnerability/CVE-2026-66307
vendor-advisory, patch
Sources
- CVE List CVE-2026-66307
- NVD CVE-2026-66307
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.